(a) Technical Field
The present invention relates to a system for fixing carbon dioxide contained in an exhaust gas. More particularly, it relates to a system for fixing carbon dioxide by extracting an alkali metal component from a raw slag and reacting the extracted alkali metal component with carbon dioxide to produce a carbonate precipitate which is separated by a submerged membrane unit.
(b) Background Art
Exhaust gases including carbon dioxide in many fields of industry are required to be treated for environmental consideration. A typical process of treating an exhaust gas includes a separation/recovery process and a fixation (immobilization) process.
The fixation process aims to convert carbon dioxide to a carbon-containing compound (e.g., carbonate) and convert the carbon-containing compound to a compound that is applicable to other industrial processes, thereby being able to remove carbon dioxide, which is known to cause global warming, in an environmental-friendly way and utilize carbon dioxide as a useful material.
To date, a single reactor in which alkali metal component extraction from a raw slag is performed concurrently with carbonation reaction has been used. However, in this conventional method, because the alkali metal component extraction and the carbonation reaction are performed concurrently, an extracted alkali metal component is carbonated, the carbonated component is formed as a precipitate, and the carbonate precipitate is then accumulated on the surface of the slag, which causes the alkali metal component extraction to be hindered, the carbonation reaction to take longer time, and the carbonation rate to be decreased.
Further, in the conventional method, because the slag, carbonate precipitate, and residual process water/solution co-exist, it is difficult to reuse process water/solution and a chemical solvent (e.g., acetic acid) used for extraction.
Therefore, as a conventional method, there has been used a method wherein alkali metal component extraction, carbonate conversion by carbon dioxide injection, and filtration for solid/liquid separation are performed in separate batches in the sequential order as shown in FIG. 3.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.